The new cultivar of blackberry called ‘APF-77’ is described herein. The new cultivar originated from a hand-pollinated cross of APF-12 (U.S. Plant Pat. No. 16,989)×Arapaho (U.S. Plant Pat. No. 8,510) made in 2001. The seeds resulting from this controlled hybridization were germinated in a greenhouse in the spring of 2002 and planted in a field near Clarksville, Ark. (West-Central Arkansas). The seedlings fruited in the summer of 2003 and one seedling, designated APF-77, was selected for its primocane-fruiting performance with attractive, large fruit with excellent flavor, excellent plant health, and erect canes.